Blot fresh marker stains with a paper towel.
Add a drop of dish soap to a damp rag, and blot the stain. Many washable markers can be lifted with mild soap. Continue until you remove as much of the ink as possible.
Soak the edge of a paper towel in non-acetone nail polish remover, and blot any leftover stain.
Wipe the area with damp, soapy rag, then rinse the rag, and use it to remove any soap residue. Let the upholstery air-dry.